Originally Posted by Gregory891

Actually no, ride is a function of many factors that influence shell, chassis and suspension harmonics.

Tire height (profile or aspect ration) actually dampens the ride, so if you upgrade (I'm using the E53 as I own one) from the basic 17" tires (65 aspect ratio) to the 19" option (50 aspect front and 45 aspect rear) or the iS spec 20" (40 aspect ratio), your ride WILL become rougher. Aspect ratio is the issue as well as the tire width (more sensitive to road imperfections due to the wider footprint).

Similarly a larger diameter sway bar will also cause a firmer ride as it will constrain the suspension (to a degree).

Lowering the car might cause the same for several reasons. The main one is that lowering is frequently done with shorter springs which usually have a firmer rate vs. relocating the spring perch lower (threaded coil-overs allow you to do this in theory with stock springs although few do this). You can find other reasons as well.

The height differences (VERY helpful) in rickybobby's chart are useful and you'll note that when you go the big / WIDE wheels, they add some height - to improve comfort lost due to the lower aspect ratio AND since inner wheel clearance is reduced.

Back to bdriven's issues: I'd suggest you set your car to the height settings for your suspension (sport or stock) and check your tire pressures as well. Both are likely your issues. Example: raise your pressure from 32 to 40 psi and you WILL notice a change.